KdgR, an IClR Family Transcriptional Regulator, Inhibits Virulence Mainly by Repression of hrp Genes in Xanthomonas oryzae pv. oryzae

Abstract

KdgR has been reported to negatively regulate the genes involved in degradation and metabolization of pectic acid and other extracellular enzymes in soft-rotting Erwinia spp. through direct binding to their promoters. The possible involvement of a KdgR orthologue in virulence by affecting the expression of extracellular enzymes in Xanthomonas oryzae pv. oryzae, the causal agent of rice blight disease, was examined by comparing virulence and regulation of extracellular enzymes between the wild type (WT) and a strain carrying a mutation in putative kdgR (⌬Xoo0310 mutant). This putative kdgR mutant of X. oryzae pv. oryzae showed increased pathogenicity on rice without affecting the regulation of extracellular enzymes, such as amylase, cellulase, xylanase, and protease. However, the mutant carrying a mutation in an ortholog of xpsL, which encodes the functional secretion machinery for the extracellular enzymes, showed a dramatic decrease in pathogenicity on rice. Both mutants of kdgR and of xpsL orthologs showed higher expression of two major hrp regulatory genes, hrpG and hrpX, and the genes in the hrp operons when grown in hrp-inducing medium. Thus, both genes were shown to be involved in repression of hrp genes. The kdgR ortholog was thought to suppress virulence mainly by repressing the expression of hrp genes without affecting the expression of extracellular enzymes, unlike findings for the kdgR gene in soft-rotting Erwinia spp. On the other hand, xpsL was confirmed to be involved in virulence by promoting the secretion of extracellular enzymes in spite of repressing the expression of the hrp genes.

Molecular control of gene expression byBrucellaBaaR, an IclR-family repressor

“…Cultured THP-1 macrophage-like cells were infected (multiplicity of infection = 100) with WT and ∆baaR B. abortus strains. No significant differences in WT and ∆baaR CFU recovered from infected THP-1 cells were observed at any time point evaluated (1,24, and 48 hours post infection), suggesting that BaaR and bab2_0213-bab2_0217 repression are not required for entry or replication in a THP-1 in vitro infection model ( Figure 10). This result is consistent with a previous study in which Brucella melitensis 16M with deletion of a gene orthologous to baaR, BMEII1022, was not attenuated in mouse spleen colonization at 1 week post infection (62).…”

“…Gene bab2_0215, which encodes a predicted IclR-family transcriptional regulator, was identified as having significantly reduced expression in a σ E1 deletion strain (∆rpoE1) (4). IclR proteins are conserved across bacteria and archaea and have been reported to control the transcription of genes involved in a range of processes (11)(12)(13), including carbon catabolism (14-20), biofilm formation (21), quorum sensing (22, 23), virulence (24)(25)(26), stress response (27), antibiotic resistance (28,29), amino acid and secondary metabolite biosynthesis (30)(31)(32), motility (33), and sporulation (34,35). However, the functional roles of IclR-family regulators in Brucella spp.…”

Regulation of Pathogenicity-related Genes in Phytopathogenic Bacteria and Plant

“…In our laboratory, we found lrp 12 , XAC4131 (a putative TonB-dependent transducer) 1 and even KdgR 16 were also involved in regulating hrp genes in the case of Xanthomonas oryzae pv. oryzae (Xoo).…”

Identification, Characteristics and Mechanism of 1-Deoxy-N-acetylglucosamine from Deep-Sea Virgibacillus dokdonensis MCCC 1A00493

“…oryzae strains (KACC10331, MAFF311018, and PXO99A) have been reported [ 4 , 5 , 6 ], and a series of genes and regulatory proteins associated with pathogenesis have been found in X. oryzae pv. oryzae [ 7 , 8 , 9 ]. In addition, many blight resistance genes also have been identified in rice [ 10 ], and the unique rice- X. oryzae pv.…”